JPH07211B2 - Head forming method for fixing end of PC stranded wire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a tension material for stress introduction in a prestressed concrete construction method, an end portion of a PC steel stranded wire used for a tensile cable of a cable-stayed bridge, and the like. The present invention relates to a method for forming a head portion for fixing an end portion of a PC steel strand, which forms a head portion having a bulged outer diameter for fixing.

(Prior art) Conventionally, stress introduction of prestressed concrete construction method,
For PC steel materials used for tensile cables such as cable-stayed bridges, PC steel rod consisting of one single wire and PC made by twisting multiple single wires
Steel stranded wire is used.

In addition, there are wedge fixing, nut fixing, and head fixing as the end fixing methods of PC steel. The wedge fixing is to fix by fixing the outer circumference of the PC steel material by the holding force when the half wedge is pulled into the tapered hole by the tensile force after the stress is introduced, and the nut fixing is to fix the screw on the outer circumference of the PC steel material. It is molded, and a nut is screwed into this and fixed. Further, in the head fixing, the end portion of the PC steel material is deformed under pressure, and a head having an expanded outer diameter is integrally provided, and the head is fixed by this head. And conventionally, all of the above-mentioned fixing methods are used for PC steel rods, but conventionally for PC steel strands,
Since the screw processing and head forming processing required for fixing could not be performed, only wedge fixing was used.

Therefore, the present inventors have developed a method of forming a head by fitting a sleeve to the end of the PC steel wire and deforming it under pressure in order to carry out the head fixing method on the PC steel wire ( JP-A-2-75430).

(Problems to be Solved by the Invention) In the above-described method of fitting the sleeve and press-molding the head, the outer diameter of the sleeve itself is largely bulged at the time of molding the head, but the PC steel stranded wire is used. Each single wire that makes up is
Since the tips are deformed in a state where they are bent in the direction of expanding each other, the sleeve easily breaks, and even if it does not burst, the strength of the bulge is smaller than the strength of the PC steel wire, and the required tension There is a problem that it cannot withstand the fixation when the force is applied.

In view of the conventional problems as described above, the present invention is a method for forming a head portion for fixing an end portion of a PC steel wire capable of forming an end fixing head for a PC steel wire having a strength equivalent to that of the PC steel wire. The purpose is to provide.

(Means for Achieving the Problem) The feature of the present invention for solving the above-mentioned conventional problems and achieving the intended purpose is that the outer circumference of the end of a PC steel strand in which a plurality of strands are twisted together. In the method of forming a head part for fixing the end of a PC steel stranded wire, in which a metal sleeve is fitted to and the fitting part of the metal sleeve is heated and deformed by heating to a temperature at which the strength of the PC steel wire does not decrease. , The metal sleeve is molded from a steel material substantially the same as the PC steel wire, and
The metal sleeve has a bottomed tubular shape with one end closed.

In addition, the PC steel stranded wire is made by assembling multiple strands of circular cross section, and the twisted strands are cold drawn to reduce the spiral groove between the strands. Any of those plastically deformed into a shape close to a circle may be used.

(Operation) According to this method, when the metal sleeve is fitted to the end of the PC steel wire and the end surface is pressed, the strands at the tip of the PC steel wire are deformed in the direction of expansion. At the same time, the metal sleeve is compressed in the axial direction and the outer circumference bulges. At this time, since the tip of the metal sleeve is closed, the end closing wall portion and the outer peripheral wall portion of the metal sleeve bite between the expanded strands to form a dense head and support the head. When pulled,
There is no deformation in the diameter reduction direction before shearing.

(Example) Next, the Example of this invention is described about drawing.

In the present invention, the PC steel strand to which the head forming process is applied is the first
As shown in the figure, twisted multiple strands of PC steel strand 1
And, although not shown in the figure, the PC steel strand 1 is plastically deformed by cold drawing to reduce the spiral groove width between the strands as shown in FIG. 2 and increase the outer cylindrical area. Let
Use PC steel stranded wire 1A.

Next, a head machining process for the above-mentioned PC steel strands 1 or 1A (hereinafter simply referred to as 1) will be described in order.

First, PC steel strand 1 is cut into a required length.

As shown in FIGS. 3 to 5, a metal sleeve 2 having a bottomed cylindrical shape is fitted to the tip head forming processing portion of the PC steel wire 1 cut to the required length. The sleeve 2 is made of the same steel material as the PC steel strand 1.

The PC steel stranded wire 1 into which the sleeve 2 is inserted is sent to a head forming machine as shown in FIG. 6 and clamped by a clamp 3. At the same time as completely clamping, the high-frequency induction heating device heating coil 4 heats the PC steel wire 1 head forming part including the sleeve 2 to a predetermined temperature.
The heating temperature is adjusted by the heating time and the heating voltage. After heating to a predetermined temperature, the heating voltage is cut off, and then the hydraulic press cylinder is actuated to push out the head-forming press fitting 5 and axially press it from the end surface of the sleeve 2. As a result, the head 6 is molded as shown in FIG. After the head forming process is completed, the press fitting 5 is returned to its original position by the hydraulic press cylinder, the clamp 3 is opened, and the wire 1 is taken out from the PC steel. Note that these operations are sequentially and automatically performed by the automatic control mechanism.

As shown in FIG. 7, the head 6 formed in this manner is curved in a direction in which the ends of the individual strands 1a of the PC steel strand 1 are expanded and the outside thereof is the cylindrical wall of the sleeve 2. It digs into the inner surface of part 2a. On the other hand, when the sleeve 2 is compressed, it deforms in the direction in which the outer peripheral surface of the cylindrical wall portion 2a swells, and the end blocking wall portion 2b of the sleeve 2 bites between the expanded strands 1a to end the strands. A head 6 having a dense interior is formed while keeping the parts immovable.

Further, the cylindrical wall portion 2a of the sleeve 2 is deformed in the diameter-reducing direction by the compressive force of the clamp 3, and the outer periphery of the PC steel wire 1 is clamped, so that the fixing force of the sleeve 2 can be increased.

Note that the heating method of the head forming processing section may be a direct energization method or another heat source instead of the high frequency induction heating method.

When the PC steel strand 1 having the head 6 thus formed is used, it can be fixed by the same method as the head fixing of the conventional PC steel rod.

It should be noted that although seven PC stranded wires are used in the above-described embodiment, the present invention is not limited to this, and PC steel stranded wires of various numbers can be used.

(Effect of the invention) As described above, the head forming method for fixing the end portion of the PC steel wire of the present invention is performed by fitting the bottomed cylindrical metal sleeve to the end portion of the PC steel wire and pressurizing and deforming. By doing so, the ends of the strands of PC steel wire expanded by the pressure and the sleeve bite into each other to form a head with a dense interior, and the PC Since the same steel material as the stranded steel wire is used and heating is performed to the extent that strength does not decrease, the strength of the head is the same as that of the PC steel stranded wire itself.

Thus, by using the method of the present invention, head fixing is realized as in the case of PC steel rods, and the cost for fixing is significantly reduced and reliable compared with the conventional wedge fixing of PC steel strands. However, the effect is enormous.

[Brief description of drawings]

1 and 2 are end views of a PC steel strand to be processed in the present invention, and FIGS. 3 and 4 are cross-sectional views showing a state in which a metal sleeve is inserted into the PC steel strand, respectively. Is a vertical plan view of the same, FIG. 6 is a cross-sectional view showing a schematic configuration of the head forming machine, and FIG. 7 is a cross-sectional view of the head forming machine when the head forming process is completed. 1,1A ... PC steel stranded wire, 1a ... stranded wire, 2 ... sleeve, 2a
...... Peripheral wall, 2b ...... End closing wall, 3 ...... Clamp, 4
...... High frequency induction heating coil, 5 ...... Heating molding metal fittings, 6 ...... Head.

Claims (2)

[Claims] 1. A metal sleeve is fitted onto the outer periphery of the end of a PC steel wire in which a plurality of strands are twisted together, and the metal sleeve fitting portion is heated to a temperature at which the strength of the PC steel wire does not decrease. In a head forming method for fixing an end portion of a PC steel stranded wire which is heated and deformed under pressure, the metal sleeve is formed of a steel material that is substantially the same as the PC steel strand, and the metal sleeve is closed at one end. A head forming method for fixing the end portion of a PC steel stranded wire characterized by having a bottomed cylindrical shape. 2. A PC steel stranded wire in which a twisted wire formed by twisting a plurality of wires is cold drawn to reduce the spiral groove width between the wires and plastically deforms the cross section into a shape close to a circle. The head forming method for fixing the end portion of the PC steel wire according to claim 1, which is used.